posted on 2018-08-16, 09:57authored byCostanza Morino, Susan J. Conway, Matthew Balme, John HillierJohn Hillier, Colm J. Jordan, Thorsteinn Saemundsson, Tom Argles
Debris flows are fast-moving gravity flows of poorly sorted rock and soil, mixed and
saturated with water. Debris-flow initiation has been studied using empirical and
experimental modelling, but the geomorphic changes, indicative of different triggering
processes, are difficult to constrain with field observations only. We identify signatures to distinguish two different debris-flow release styles by integrating high-resolution multi temporal remote sensing datasets and morphometric analysis. We analyse debris flows sourced above the town of Ísafjörður (Iceland). Two debris-flow triggering processes were previously hypothesized for this site: (i) slope failure, characterised by landslides evolving into debris flows, and (ii) the fire-hose effect, in which debris accumulated in pre-existing, steep-sided bedrock passages is transported by a surge of water. It is unknown which process dominates and determines the local risk. To investigate this question, we compare
airborne LiDAR elevation models and aerial photographs collected in 2007 with similar
data from 2013. We find that two new debris-flow tracks were created by slope failures.
These are characterised by steep sliding surfaces and lateral leveed channels. Slope
failure also occurred in two large, recently active tracks, creating the preparatory
conditions for the fire-hose effect to mobilise existing debris. These tracks show alternating zones of fill and scour along their length, and debris stored below the source-area at rest angles >35°. Our approach allows us to identify and quantify the morphological changes produced by slope failure release process, which generated the preparatory conditions for the fire-hose effect. As debris flows are rarely observed in action and morphological changes induced by them are difficult to detect and monitor, the same approach could be applied to other landscapes to understand debris-flow initiation in absence of other monitoring information, and can improve the identification of zones at risk in inhabited
areas near hillslopes with potential for debris flows.
History
School
Social Sciences
Department
Geography and Environment
Published in
Earth Surface Processes and Landforms
Citation
MORINO, C. ... et al., 2018. Debris-flow release processes investigated through the analysis of multi-temporal LiDAR datasets in north-western Iceland. Earth Surface Processes and Landforms, 44 (1), pp.144-159.
This work is made available according to the conditions of the Creative Commons Attribution 4.0 International (CC BY 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by/4.0/
Acceptance date
2018-08-12
Publication date
2018
Notes
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.